Fluorine-containing borate glass compositions

ABSTRACT

There is disclosed fluorine-containing glass compositions which are lead-free and which have utility as sealing glasses, especially for iron-sealing applications, and which are useful as a frit. The glasses generally have the following compositions in percent by weight: about 5-11 percent SiO2; about 37-53 percent B2O3; about 5-12 percent ZnO; about 2-5 percent Al2O3; about 4-18 percent Na2O; about 2-6 percent K2O; about 2-13 percent Li2O; about 3-6 percent CaO; about 3-6 percent BaO; and fluorine in an amount not to exceed about 3.5 percent.

United States Patent Jaroslaw Kohut Parma Heights, Ohio 81 9,473

Apr. 25, 1969 Oct. 26, 1971 Owens-Illinois, lnc. Toledo, Ohio Inventor Appl. No. Filed Patented Assignee FLUORINE-CONTAINING BORATE GLASS COMPOSITIONS 6 Claims, No Drawings U.S. Cl 106/54,

106/48 Int. Cl C03c 3/04 Field of Search 106/54, 39,

References Cited UNITED STATES PATENTS 9/1961 Cianchi 106/39 3,290,535 12/1966 Hirayama 106/54 X 3,312,556 4/1967 Oikawa et a1 106/54 3,379,942 4/1968 Davis 106/54 X 3,392,312 7/1968 Carman 106/54X Primary ExaminerTobias E. Levow Assistant Examiner-W. R. Satterfield AttameysDonald K. Wedding and Edward J. Holler FLUORINE-CON'IAINING BORATE GLASS COMPOSITIONS THE INVENTION This invention relates to glass compositions and, more particularly, to lead-free glass compositions having relatively low softening temperatures. The glasses of this invention have their major utility as sealing glasses and especially as sealing glasses for iron. They may also be employed as a frit in which electroluminescent phosphors may be suspended and applied onto a suitable electrode for purposes of forming an electroluminescent phosphors may be suspended and applied onto a suitable electrode for purposes of forming an electroluminescent phosphor-bearing enamel.

Heretofore, glasses which have been suitable for the above purposes typically contain substantial amounts of lead oxide. It is generally known that the manufacture of these prior art lead-bearing glasses are subject to certain major deficiencies. One of these deficiencies is the fact that the cost of lead-containing batch material is relatively expensive and, therefore, these glasses become somewhat uneconomical for substantial commercial usage. In addition to the high raw material costs, the cost of producing lead-bearing glass is increased still further because of the corrosion and/or erosion of the furnace refractories during the melting operation. Additionally, the conditions under which melting of a lead-bearing glass takes place must be well controlled. That is, the lead-bearing glass must be melted under a controlled oxidizing atmosphere. Similarly, when lead glasses are used for sealing applications, it is generally important that the atmosphere under which the scaling is done, also be a controlled oxidizing atmosphere. Another deficiency of employing and manufacturing leadbearing glasses resides in the fact that lead compounds are highly toxic and therefore undesirable to use. When used, glasses containing lead must be melted with special precautions due to the toxicity of the lead compounds.

Those skilled in the art readily appreciate the need for glass compositions which do not possess the hereinbefore stated deficiencies of the prior art lead glasses.

It is, therefore, an object of this invention to provide glass compositions which can be economically produced.

It is another object of this invention to provide glass compositions which may be melted without the need for con trolling the atmosphere under which the glass is melted.

It is another object to provide substantially transparent glass compositions which have linear coefficients of thermal expansion in the range of about 1 10x10" to 120x10" centimeters per centimeter per degree C. over a temperature range of about C. to 300 C.

Yet another object is to provide a lead-free glass.

Still another object of this invention is to provide for glasses which have relatively low softening temperatures, that is, preferably a softening temperature of less than about 510 C. and, most desirably, softening temperatures of less than about 480 C.

Yet another object of this invention is to provide for a substantially transparent sealing glass.

Still another object of this invention is to provide sealing glasses for making glass-to-metal seals, wherein the sealing operation may be done under either oxidizing or reducing conditions.

The foregoing objects and other advantageous features of this invention are advantageously obtained by employing glass compositions having the following constituents in percent by weight: SiO- .about -l l; B,O about 37-53; ZnOabout 5-12; Al,O about 2-5; Na,Oabout 4-18; K Oabout 2-6 Li,Oabout 2-13; CaO-about 3-6; BaO-about 3-6; and fluorine in percent by weight not to exceed about 3.50. Preferably, the glass compositions of this invention will contain the following constituents in parts by weight: SiO,about about 2.6-4.8; Na Oabout 6-l4.l; K Oabout 2.2-5.4; Li O-about 2.8-ll.5; CaO-about 4-5; BaO-about 4-5; and fluorine in percent by weight not to exceed about 3.50. Most desirably, the glass will have the following approximate compositions in percent by weight: SiO 6-7; A1 0 2.6-2.9; Na O-6-l4 .l; K O2.2 -5.4; CaO4.6 -4.9; BaO- 4.6-4.9; B O;,49-5O; Li O3.2-l1.5; ZnO-7-l0.l; and fluorine in percent by weight not to exceed about 3.50.

The raw materials which are employed to manufacture the foregoing glasses of this invention are those typically used in the commercial production of various glass compositions. That is, the raw materials include sand, sodium silica fluoride, alumina, soda ash, potash, lime, barium carbonate, boric acid, lithium carbonate and zinc oxide.

Table l, hereinafter, represents glass batch ingredients in parts by weight whichmay be employed to produce the advantageous glass compositions of this invention. It will, of course, be apparent that these compositions are merely exemplary of applicant's invention and are in no way to be construed as limiting the scope of this invention.

TABLE l Material A B C D Sand 410 233 233 233 Sodium Silica Fluoride 208 292 292 29: Alumina 237 I37 I37 I37 Soda Ash 796 1,044 436 35s Potash 355 392 CH8 1?! Lime 430 430 430 4.10

Barium Carbonate 3l0 3 l0 1H0 Borie Acid 4,417 4,417 4.4l7 4,417 Lithium Carbonate 358 420 L420 L420 Zinc Oxide 353 353 355 504 The final glass may be prepared from the foregoing batch compositions in any conventional manner. That is, the batch ingredients are first admixed and then melted in a suitable melting furnace. Thus, the batch compositions of this invention were first admixed and placed in suitable crucibles; the batch-containing crucible was then positioned in an electrically fired furnace and heated to about 2,400 F. for about 8 hours to obtain a homogeneous melt. According to techniques well known to those skilled in the art, the melted glass was then cooled and pulverized to produce a particulate glass suitable for use as a sealing glass. If desired, the batch may also be melted in a gas-fired furnace and, as pointed out above, .there will be no need to control the redox state of the not gases.

The glasses resulting from the melting of the above batches have the compositions set forth in table ll, in percent by weight, if calculated from the respective batches on the customary theoretical oxide basis. It will be understood, however,

. that the fluorine remaining in the glass is most likely combined as the fluoride of one or more of the cationic constituents of the glass and, most likely, issues in the form of sodium fluoride. The fluorine contents in table II are recited in the usual manner as being additional to the compositions of the base glasses and represent the maximum percent by weight of fluorine which could be present if no fluorine were lost in the melting. The properties stated in table ll were measured on ac- 1n general, the glass compositions formed in accordance with this invention will be advantageously relatively low-softening temperature glasses. That is, they will have softening temperatures below about 510 C.; preferably, the softening temperature of the glasses will be below about 480 C. and most desirably will have softening points in the range of about 440 C. to about 480 C. As used herein, the term softening point, or softening temperature," means that temperature at which a uniform flber, 0.5 to 1.0 mm. in diameter and 22.9 cm. in length elongates under its own weight at a rate of 1 mm. per minute when the upper 10 cm. of its length is heated. For

glasses of this invention, the softening point or temperature generally corresponds to that temperature at which the base 10 logarithm of viscosity is about 7.65. Additionally, these glass compositions will most desirably have coefficients of thermal expansion, when measured over a range of about C. to 300 C., of about 110 to 120 10 cm./cm./ C. Those skilled in the art will immediately recognize that these features of the inventive glass compositions make the glasses well adapted for use in making glass-to-metal seals, especially glass-to-iron seals. Additionally, as was surprisingly found by applicant, the inventive glasses disclosed herein will be clear, notwithstanding the relatively high-fluorine contents. Normally, as will be readily apparent to those skilled in the art, glasses having fluorine contents comparable to those disclosed herein are milky or opallike in appearance.

Since, in the analysis of fluorine containing glass compositions, it is standard practice to determine the cationic constituents of a glass, which are reported on an oxide basis, and then to determine the amount of fluorine present, which is reported as fluorine along with the oxygen equivalent thereof, a fluorine containing glass may be looked upon as a glass having a base composition and a fluorine content. The base composition, or the base glass, of course, is that composition which is ascertained by determining the quantity of the various cationic constituents of the glass and reporting them on an oxide basis; it being understood, of course, that portions of some of the cations exist, however, in the form of fluorides and not as oxides.

The fluorine content of the glasses of this invention will advantageously be about at least 0.75 percent by weight. Table 11] below represents, in addition to the fluorine content, base glass compositions of this invention on a theoretically calculated oxide basis. Column A represents glass compositions suitable for obtaining glasses having the hereinbefore described desirable features, while Column B represents preferred compositions. Most desirably, glasses will have the composition set forth in Column C.

TABLE 111 Constituent by Weight) A B C 5 sio, 5-11 6-10 6-7 .a,o, 3143 49-50 49-50 ZnO 5-12 710.l 710.1

A1,,O, 2-5 2.6-4.8 2.6-2.9 Na,0 4-18 6-14.! 6-l4.1

K,o 241 2.2-5.4 2.24.4 10 up 243 2.8-11.5 3.2-: 1.5

CaO 3-6 4-s 4.6-4.9 Bio 3-6 4-5 4.6-4.9

As pointed out above, the base glasses of table 111 will also contain fluorine in an amount not to exceed about 3.5 percent by weight and preferably will include at least about 0.75 percent by weight.

Having thus described my invention and having set forth the best mode contemplated in practicing the invention,

I claim:

I. A lead-free, fluorine-containing glass having a softening temperature of between about 440 C. and about 480 C. and a linear thermal expansion coefficient in the range of about 110x10" to 120 10" cm/cm/ C. consisting of between about 0.75 to about 3.5 weight percent fluorine and a base glass, said base glass consisting essentially of the following range of constituents in percent by weight: about 6-7% SiO,, about 49-50 B 0 about 7l0.1% ZnO, about 26-29% A1 0 about 6-l4.1% Na o, about 2.2-5.4% K 0, about 3.2-1 1.5% Li 0, about 4.6-4.9% CaO, and about 4.6-4.9% BaO.

2. A clear, lead-free, fluorine-containing glass consisting essentially of the following constituents on a theoretical oxide basis in percent by weight: about 610% SiO about 49-50% B 0 about 7-10. 1% ZnO, about 2.6-4.8% A1 0 about 6-14.1% Na O, about 2.2-5.4% K 0, about 2.8-1 1.5% Li O, about 4-5% CaO, and about 4-5% 3210, said glass having a softening point of less than about 510 C. and a fluorine content of between about 0.75 to about 3.5 weight percent.

3. The glass of claim 2 wherein said softening point is between about 440 C. and 510 C. and whereinsaid glass has a linear coefficient of thermal expansion between about 1 10 to about 120X10". v

4. A clear, relatively low-softening temperature, lead-free sealing glass consisting essentially of the following constituents in percent by weight: about 5-1 1% SiO;, about 37-53 B 0 about 5-12% ZnO, about 2-5% A1 0 about 4-18% Na,0, about 26% K 0, about 2-13% Li O, about 3-6% CaO, about 36% BaO, and fluorine in an amount between about 0.75 percent to about 3.5 percent by weight, said glass having a thermal expansion coefficient between about 1 10 to 120x 10 cm/cml" C.

5. A lead-free glass forming composition consisting essentially of the following glass forming constituents in percent by weight based on the glass fonning constituents of said compositions: about 5-1 l% SiO,, about 37-53% B 0 about 5-12 ZnO, about 2-5% A1 0 about 4-18% Na O, about 2-6% K 0, about 2-13% Li o, about 3-6% CaO, about 36% BaO, and fluorine in an amount between about 0.75 to about 3.5 percent.

6. The glass of claim 5 wherein fluorine is present in an amount of at least about 2.5 percent by weight.

t i i 1! k UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 15,772 Dated October 26, 1971 Inventor(s) Jaroslaw Kohut It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

| Ih the ABSTRACT, line 6, "811) should be --SlC --5 in the I ABSTRACT, line 6, To should be -B2O3--5 in the ABSTRACT, line 7, "A" should be --Al O --5 in the ABSTRACT, line 7, "New" should be -Ne O-3 in the ABSTRACT, line 8, HKOH should be --K O--in the ABSTRACT, lj he 8, Li0" should be -Li C--. Column l, line #7, llO x l0? should be --llC X lO column 1, line #7, 110 X 10 should be --llO x 10. Column 2, TABLE 1, line 29, "Barium Carbonate 510 Z310 510" should read Barium Carbonate BlO 51C 51C f5lO--; line 47, "not" should be -hot. Column 2, TABLE II, line 75, "Bee 4.75 4.75 #75 4.75" should b BaC A LL A376 +.75--; Column 5, line "loshould be --lO -Column 3, line 29, o X 1C should be 120 X 10- Column A, line 2%, X 10 to l20 X lo should be 1 --llO X 10 to l2o X Column A, line A2, X lo should read --l2O X 10 Column 4 lines 50 and El, llO to 120 X 10 should be --llO to 120 X 10- aligned and Sealed till :1 1th Hey of New 1972.

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2. A clear, lead-free, fluorine-containing glass consisting essentially of the following constituents on a theoretical oxide basis in percent by weight: about 6-10% SiO2, about 49-50% B2O3, about 7-10.1% ZnO, about 2.6-4.8% Al2O3, about 6-14.1% Na2O, about 2.2-5.4% K2O, about 2.8-11.5% Li2O, about 4-5% CaO, and about 4-5% BaO, said glass having a softening point of less than about 510* C. and a fluorine content of between about 0.75 to about 3.5 weight percent.
 3. The glass of claim 2 wherein said softening point is between about 440* C. and 510* C. and wherein said glass has a linear coefficient of thermal expansion between about 110 to about 120 X 10
 7. 4. A clear, relatively low-softening temperature, lead-free sealing glass consisting essentially of the following constituents in percent by weight: about 5-11% SiO2, about 37-53% B2O3, about 5-12% ZnO, about 2-5% Al2O3, about 4-18% Na2O, about 2-6% K2O, about 2-13% Li2O, about 3-6% CaO, about 3-6% BaO, and fluorine in an amount between about 0.75 percent to about 3.5 percent by weight, said glass having a thermal expansion coefficient between about 110 to 120 X 10 7 cm/cm/* C.
 5. A lead-free glass forming composition consisting essentially of the following glass forming constituents in percent by weight based on the glass forming constituents of said compositions: about 5-11% SiO2, about 37-53% B2O3, about 5-12% ZnO, about 2-5% Al2O3, about 4-18% Na2O, about 2-6% K2O, about 2-13% Li2O, about 3-6% CaO, about 3-6% BaO, and fluorine in an amount between about 0.75 to about 3.5 percent.
 6. The glass of claim 5 wherein fluorine is present in an amount of at least about 2.5 percent by weight. 